Tamoxifen Prevents Apoptosis and Follicle Loss from Cyclophosphamide in Cultured Rat Ovaries1

Abstract

Recent studies documented that the selective estrogen receptor modulator tamoxifen prevents follicle loss and promotes fertility following in vivo exposure of rodents to irradiation or ovotoxic cancer drugs, cyclophosphamide and doxorubicin. In an effort to characterize the ovarian-sparing mechanisms of tamoxifen in preantral follicle classes, cultured neonatal rat ovaries (Day 4, Sprague Dawley) were treated for 1-7 days with active metabolites of cyclophosphamide (i.e., 4-hydroxycyclophosphamide; CTX) (0, 1, and 10 μM) and tamoxifen (i.e., 4-hydroxytamoxifen; TAM) (0 and 10 μM) in vitro, and both apoptosis and follicle numbers were measured. CTX caused marked follicular apoptosis and follicular loss. TAM treatment decreased follicular loss and apoptosis from CTX in vitro. TAM alone had no effect on these parameters. IGF-1 and IGF-1 receptor were assessed in ovarian tissue showing no impact of TAM or CTX on these endpoints. Targeted mRNA analysis during follicular rescue by TAM revealed decreased expression of multiple genes related to inflammation, including mediators of lipoxygenase and prostaglandin production and signaling (Alox5, Pla2g1b, Ptgfr), cytokine binding (Il1r1, Il2rg ), apoptosis (Tnfrsf1a), second messenger signaling (Mapk1, Mapk14, Plcg1), as well as tissue remodeling and vasodilation (Bdkrb2, Klk15). The results suggest that TAM protects the ovary from CTX-mediated toxicity through direct ovarian actions that oppose follicular loss.

Ovarian damage from chemotherapy and current approaches to its protection

“…Most of our understanding of precisely how CPM induces ovarian damage has come from studies trying to prevent that damage (Table 1). As expected, given what is known about its action on cancer cells, there is clear evidence that CPM leads to an upregulation in apoptosis in the ovary, as is evident from the rapid induction of DNA breaks (Piasecka-Srader et al., 2015) and from a change in the expression levels of pro- and anti-apoptotic genes (Petrillo et al., 2011; Pascuali et al., 2018; Luan et al., 2019). Recent studies have demonstrated that the DNA damage-induced pro-apoptotic protein PUMA plays a key role in inducing oocyte apoptosis in rodents following CPM treatment (Nguyen et al., 2018), as is also the case following irradiation (Kerr et al., 2012).…”

“…As with the clinical work, CPM was the first drug shown to induce ovarian damage and follicle loss in the mouse (Miller and Cole, 1970), and CPM exposure is regularly used as a pre-treatment to induce widespread follicular atresia in a variety of experiments where the research examines the physiology of an ovary devoid of follicles (see, for example, Goldman et al., 2017; Kano et al., 2017; Melekoglu et al., 2018; Tsuyoshi et al., 2015). For growing follicles, there is now a large body of evidence linking CPM exposure to follicle atresia and granulosa cell apoptosis (Jarrell et al., 1991; Ezoe et al., 2014; Piasecka-Srader et al., 2015; Yuksel et al., 2015; Chen et al., 2016). Exposure of growing follicles to CPM, particularly at earlier stages, has also been linked to embryo abnormalities and to malformation in the next generation in later pregnancies (Barekati et al., 2008; Meirow et al., 2001, respectively).…”

Impact of Taxanes, Endocrine Therapy, and Deleterious Germline BRCA Mutations on Anti-müllerian Hormone Levels in Early Breast Cancer Patients Treated With Anthracycline- and Cyclophosphamide-Based Chemotherapy

“…Similarly, higher AMH values in patients treated with tamoxifen following chemotherapy has been also observed in two recent studies (8, 23), with one of them showing a faster AMH recovery between 3 and 6 months after the end of systemic cytotoxic therapy for women treated with endocrine therapy (23). Notably, when given concurrently with chemotherapy, preclinical studies have suggested a potential protective effect of tamoxifen against anticancer treatment gonadotoxicity, including of cyclophosphamide-based therapy (24). Taken together, although tamoxifen may cause perturbation in menstrual function after chemotherapy, the available evidence including our findings suggests the lack of detrimental effect on patients' ovarian reserve.…”

Impact of tamoxifen therapy on fertility in breast cancer survivors

“…More recently, additional evidence has suggested that tamoxifen can prevent follicle loss when administered concurrently with gonadotoxic agents (e.g. cyclophosphamide) (31); however, concurrent treatment is not used to treat breast cancer due to increased risk of adverse side effects and the possibility of treatment interactions (31). …”